MONILIGASTER GRANDIS, A. G. B. 345 
to take its place among the columnar cells. These gland- 
cells do not occur near the external aperture; the glandular 
mass formed by them constitutes the “ prostate ;’? a layer of 
muscle, the fibres of which run in various directions, overlies 
the epithelial layer ; outside this comes the thick layer formed 
by the deep-lying glandular portions of the prostatic cells; out- 
side this is another layer of muscle, and outside this the ordi- 
nary layer of coelomic epithelium. The nuclei of these 
epithelium-cells can be seen with difficulty in sections, but the 
presence of the cells themselves may be very clearly demon- 
strated by the use of silver nitrate. 
The sperm-duct penetrates the prostate, and then opens into 
the atrium at the point furthest from the male pores (fig. 55). 
Ovaries, Oviducts, and Ovisacs.—The ovaries lie in 
Segment x1, or rather in that closed portion of the segment 
which contains also the nephridium ; they are not therefore 
exposed in an ordinary dorsal dissection. When the septum 
is cut so as to expose them, they are seen as large, brilliantly 
white, frill-like organs ; they really lie above.and at the side of 
the csophagus, and not near the ventral wall. They are as 
much as 3 inch long and 4 inch deep. Each is really a very 
closely-set zigzag, the free edge of which is slightly lobed and 
thicker than the attached edge owing tothe greater development 
of the ova which are set free from the free edge (figs. 50 and 57). 
The oviduct is merely a modification of a portion of Septum 
x1-xi1. There is nothing standing out freely into the segment. 
The epithelium is thickened and thrown into folds and ciliated, 
and as the wall is very thin in the intersegmental region, there 
is a very short little duct running to the exterior ; the aperture, 
as mentioned above, is strictly intersegmental. The ovisacs 
are diverticula of that portion of Septum x1-x1 which forms 
part of the wall of the sac containing the ovaries and nephridia 
of Segment x1; they, and indeed the whole sac, become packed 
with ova; the pair of ovisacs and this portion of Segment x1 
thus packed are shown of natural size in fig. 51. A young 
ovisac just developing is shown in fig. 59. The wall becomes 
thick and very vascular, and when packed with ova there is an 
